The idea is to have additional housing bonus rooms that are provided to everyone in the town. Think of it like a Culture property but you can have a "Hospital" property type that you put bedroom/seating/lighting furniture into and new "Hospital" type furniture.

Some other property types could be Library/School and Courthouse. Think town infrustrastructure, like how people in real life want to live near a good school and hospital. Something a town can invest in that benifits all players in that town through the housing bonus system.

For Countries and Federations, you could apply the property to all members as well with the normal additional room bonus reductions with the best providing the full benefit.